1. Field of the Invention
The present invention relates to missiles. More specifically, the present invention relates to optically-aided missiles.
2. Description of the Related Art
Tube launched, optically-tracked, wire-guided (TOW) type missiles, Stinger type missiles and other such optically-aided type missiles in service today typically use launcher mounted optical instruments for missile guidance. Typically the gunner places cross-hairs of the Optical Guidance System (OGS) on the target and pulls the trigger. In fractions of a second, the missile comes into the OGS's field-of-view and the OGS's tracking algorithms begin tracking the missile and measuring the missile's angular displacement to the OGS's cross-hairs. The angular displacement measurement is then used in accordance with a guidance law by a navigation system and an autopilot to guide the missile to the target.
Conventional optical guidance systems were designed for short missile standoff ranges. The accuracy of conventional missiles degrades as range-to-target increases. This is due to the fact that a small angular error in the OGS measurement produces a large position error at long ranges. The angular measurement errors are caused by OGS boresight errors, as well as tracker noise and gunner motion. The OGS boresight errors are caused by optical misalignments and are expensive to abate. Consequently, weapon system performance of conventional optically guided missiles at long ranges is limited by the position error effects of OGS tracker noise and gunner motion.
Unfortunately, longer standoff ranges will be required in the future and current guidance systems are not expected to meet the projected terminal guidance (miss distance) accuracy requirements of same.
Another drawback of the weapon systems described above is that the launcher has to continuously measure and uplink the line-of-sight measurements to the missile to ensure airframe stability and terminal performance. These systems have little tolerance for launcher dropouts. This imposes excessive burdens on the optical tracking system and the uplink system. It also unnecessarily exposes the launcher to threats during the mission.
Accordingly, a need exists in the art for an optically-guided type missile design offering improved performance at long range.